One mode of windmill construction comprises a blade assembly which rotates about a generally vertical axis. Examples of such vertical axis windmills are shown in the U.S. Pat. No. 622,115 Carlson; the U.S. Pat. No. 2,038,467 Zanoski; the U.S. Pat. No. 4,115,027 Thomas; and the U.S. Pat. No. 4,032,257 de Haas. Attention is also directed to the German Pat. No. 342,778, Muhlbach issued Oct. 24, 1921; the German Pat. No. 2,602,380 Sicard, issued July 29, 1976; the British Pat. No. 13,700 Robertson issued June 9, 1903; the French Pat. No. 530,231 Rondeau, issued Dec. 21, 1921; and the French Pat. No. 2,291,381 Fassle, issued June 11, 1976.